1. Field of the Invention
The following invention relates to a device for mixing at least one aqueous fluid substance contained in a vessel having an open upper end and a closed bottom end, said device comprising a support plate adapted for receiving at least one vessel.
2. Description of the Prior Art
It is well known in the field of bio-medical analyses to use a rotating disc having a plurality of vertical holes for receiving sample tubes. The disc is surrounded by processing stations and transfers the same tubes sequentially in order to process the samples contained therein for analysis. Generally, a sample to be analyzed is brought into reaction with one or more appropriate reagents. For obtaining good and reproducible results, it is very important that the different substances put into reaction be first thoroughly mixed together. Such mixing operation is difficult to achieve in certain circumstances. Sample-to-sample carryover via any mixing device must also be avoided.
The volumes of samples used in bio-medical analyses become smaller as miniaturization of apparatuses progresses, i.e. of the order of microliters, so that the liquid surface tension becomes high with respect to the liquid weight. To ensure measurement accuracy and to avoid contamination risks, it is usually not possible to use an agitator which is brought into contact with the liquid. Ultrasonic mixing has already been proposed but is not necessarily adapted to each kind of biomedical analysis. Indeed, when used in immuno-assay techniques, for example, ultrasonic energy generates cavitation which may break the complexes formed between antigens and specific antibodies, thus introducing source of error.
GB-A-2,124,102 already discloses a shaker for vessels supported at intervals around the peripheral portion of a turntable attached to a vertical axis. The shaker is supported by a board fitted below the turntable and comprises a motor, a crank fitted to a vertical shaft of the motor and an eccentric member pivotally attached to the crank, An elevator is disposed below the board in order to engage the eccentric member with the bottom of the vessel and further, the eccentric member is rotatively driven by the motor. The drawback of such an apparatus is to necessitate two motors one for the shaker and another for lifting the board supporting the shaker, which are to be controlled from a central monitoring device.